Repaired gelcoat spots yellowing? How to fix?

Had two gouges on the hull repaired a couple years ago where the gelcoat was chipped off due to a couple dock dings. One was at the transom on the lip of the swim platform, and the other was on the forward starboard shoulder just above the rubrail on my 32 powerboat. The "reputable" local shop that did the work enlarged the areas from about the size of a quarter or half dollar to approximately 3x6" areas...The problem now is those two spots in what should be bright white gelcoat, are now noticeably yellowing.This is not organic yellowing from sitting in the water.

I've read everything from FSR, toilet bowl cleaner, On/Off etc. to wetsanding starting with 220 moving thru 400/600/1000 and finishing with 2000 grit sand paper. Other threads blames it on the oozing to the surface of the compounds like stylene? and whatever else is in it to bond.

Is there any merit to these fixes? I've never wetsanded gelcoat and it scares me a bit to scratch up the boat and not be able to get it back to a glossy finish and have to take it back to the repair to fix a self-inflicted wound.

So any new experiences or tips on new products on the market would be helpful. Any guidance on properly wetsanding a spot like this would definitely be helpful if I have to resort to doing that.

I looked up a product put out by claneashine.com that looked really promising on their website video, but they're located in Australia and the shipping costs was as much as the products.

BTW, the boat is still tucked away coccooned up or I would take and post pics.

Thanks in advance

Re: Repaired gelcoat spots yellowing? How to fix?

Aren't repair shops great . . .

My take is that the replacement gelcoat is fading faster than the original gelcoat, or at least not fading in the same direction. That is a problem that you do run into with gelcoat repairs.

You can try some "iron out" on the areas to see if it is a mineral-based discoloration . . .

Otherwise, you might want to research some additional gelcoat repair places.

Re: Repaired gelcoat spots yellowing? How to fix?

This happens quite often, the most common reason is the use of styrene and/or other thinners to reduce the viscosity of the gel coat. Gel coat is rather thick and pasty, it’s designed to be sprayed through some rather heavy duty and high pressure equipment onto the mold, not through small sprays guns that are typically used for doing repairs, so people add solvents, sometimes large amounts of them so it will spray better.

Adding these solvents allows the gel coat to spray and flow better, leaving a much smoother surface to sand on, which will reduce the time and effort needed to do the repair. The down side is that many of these solvents reduce the physical properties of the gel coat, this includes weather resistance, all of the solvents will degrade gel coat, sometimes significantly when larger amounts are added. In lab testing you can easily detect the difference when 3% styrene is added, many repair shops will add far more than this, some up to 30+%.

The poor weathering isn't noticed at first, and if the boat (repaired area) is kept indoors or covered it may take a while for the repair to discolor, but it almost always will. Most shops don't get call backs on these repairs for several reasons, sometimes the boat owner sells it before it discolors, other times if after a few years it changes they sort of accept it, or don't care, or, If the owner did it themselves they may just expect it to happen.

There are other reasons, too much or too little catalyst can do it, poor cure due to cold weather, etc.
Products are made by the gel coat manufactures to reduce the viscosity for doing patches, they are formulated to reduce the chances of having a patch discolor over time, but many places still use other solvents.

Sanding and buffing is about the only way to get rid of it, this removes the discolored surface that was exposed to UV light. The problem is the repair typically discolors again and you need to repeat the process. You can try buffing with a coarse compound before doing any sanding, sometimes it works, but if it doesn’t sanding is about the only way to remove it.

Re: Repaired gelcoat spots yellowing? How to fix?

Yeah the boat is only 6 yrs old and in otherwise pristine condition. Sux having these two spots stick out like they do against a bright white background.

Ok so I should try some coarse rubbing compound first, then on to the wetsanding gig if that dont gain results.

Would chemical products like On/Off do anythin at all to minimize using coarse products on the ifnish? And what is "Iron Out"?

I'm a little leary about wetsanding or coarse products for fear of it leaving me with a dull scratched up spot.

Re: Repaired gelcoat spots yellowing? How to fix?

Bump for more opinions/suggestions. Hopefully start insome kind of direction this weekend if the weather allows.

Re: Repaired gelcoat spots yellowing? How to fix?

What about contacting the shop who "fixed" it and hold them responsible for the “lack of” quality of their repair?!

Re: Repaired gelcoat spots yellowing? How to fix?

Plain and simple that is what happens to alot of repairs. Most manufacturers that do repairs know they will get a few years beyond warranty before any ill effects happen. Most likely because they are spraying a fresh repair on fresh gelcoat. Alot of repairs look good for a bit especially with an older finish to start with. The repair and the old gelcoat will continue to age at a different pace. Buffing and waxing etc will help it alot and really is the only remedy on a repair job or redoe it . It is usually a maintenace thing after a spot repair is done. Buff and wax on a regular basis. That is why I don't like repairs. on any gelcoat surface. It will show itself some day after the harsh uv rays.

Re: Repaired gelcoat spots yellowing? How to fix?

GoFastr said:

Bump for more opinions/suggestions. Hopefully start insome kind of direction this weekend if the weather allows.

Click to expand...

Unfortunately .. your probably going to have to respray it. Sure you can sand and buff and Possibly have it come back to color.

To answer your question on why it happened is specifically unknown .. but I can tell you a few reasons why this yellowing happens so fast.

1. It was a custom color match where they had to use a bit of yellow pigment/color to do a perfect match.

2. Styrene additive to a color match ( never a good idea to use a known yellowing solvent into a match that has mostly yellow tints/pigments added to it ).

3. Heat gun to speed up the curing. You can take years off the life of gel with a heat gun used incorrectly.

Best case is that they used a Factory matched gel. You might be able to wetsand and buff out ( though you will risk a chance on burning though the gel and see the underlying repair ).

If they used Factory gel .. then they probably reduced it with styrene and/or over mixed or heat gunned it.

If its a custom match .. then they probably didnt let the gel post cure and wash out.

The problem with color matching is that you have to understand the pigments and additives that you add.

Many of times I have had customers complain that the color match was not Good Enough. I say " Wait a few months and if you dont like it after that then I will come back and match it Perfectly ! " .. a few months later I call them up and ask how there patch is going. " Dude I cant even see it anymore .. Thanks ! "

Gel Swings ( changes colors over time ) .. Not so much a factory gel applied .. it more common on the Custom Gel matches. Sitting there for a few hours getting that gel Just right to get that paycheck is not uncommon.

Guy says " You Da Man !! " .. yea .. but its gonna Swing colors.

Custom Colors Should IMHO mostly Never perfectly match when the job is Done.

Its when the Customer ( or yourself doing it as a DIY ) says "This is not a good match" where you have to say "wait a bit .. it will" .. and if you know what your doing it will swing right into it .

What do you want .. a perfect match now .. or a perfect match for the next 5-10 years ..

I said too much already .. but you get my point ..

Peace ..

YD.

Re: Repaired gelcoat spots yellowing? How to fix?

Yacht Dr excellent explanation.

I did call the repair shop, but long story short, they want more money and to do the job over. I'm not there yet.

Experimenting I did take some "heavy duty" rubbing compond by hand on one of the spots to test it and it actually took out a lot of the yellowing. So I'm thinking if I used my small 3" electric buffer with the compound it might just take out enuff to make it "almost" invisible to the common observer.

Re: Repaired gelcoat spots yellowing? How to fix?

GoFastr said:

Yacht Dr excellent explanation.

I did call the repair shop, but long story short, they want more money and to do the job over. I'm not there yet.

Experimenting I did take some "heavy duty" rubbing compond by hand on one of the spots to test it and it actually took out a lot of the yellowing. So I'm thinking if I used my small 3" electric buffer with the compound it might just take out enuff to make it "almost" invisible to the common observer.

Click to expand...

Yea .. thats what some of them do .. more money to do it Right again. I would Never do this. I state right on my Invoices that you can expect a 5 year color match and I will come out and re-blend it for free if the patch discolors or does not come into color within a year. However that means that the owner agrees to let it "age" for a season. I cant ( and nobody can without a crisp new boat with factory gel ) custom color match a gel that will come off looking perfect expect to last that way. Just wont happen.

It will forever change colors even if you sand and polish those spots .. well most likely unless they had a Base Gel to work with .. or didnt wash the pigments out properly.

I get gel ..I know gel .. I understand its nuances and properties.

Its an art form and unless you get someone out there that can baffle you with BS or win you over with experience your at the Mercy of Them ..

Or do it ( probably gonna fail at the match and not the application ) Yourself and Learn..

YD.

Re: Repaired gelcoat spots yellowing? How to fix?

Well the heavy duty rubbing compound coupled with FSR has seemed to do a good (not great) job on the one spot I've experimented with which is the smallest of the two. 'Bout to tackle the other to see how well this method does there. Gonna break out my small 3" Turtle Wax polisher this time.

"Nuther question I have...on my forward deck I see it's looking a little dirty or more dingy vice bright white and just washing a spot with soap and pad doesn't bring it clean. Is this simply a matter of using a soft rubbing/wax compounnd to bring it clean?

Re: Repaired gelcoat spots yellowing? How to fix?

It might come back .. but it will most likely go back to a stained color ..

YD.

Re: Repaired gelcoat spots yellowing? How to fix?

Yeah well if I can get it to be less or almost not noticeable then I can maintain it by just doing this when needed vice having it goiged back out and starting over. Like I mentioned the heavy rubbing compound coupled with my 6 inch wax buffer (not 3" inch as stated earlier) has really reduced it quite a bit though not entirely. I'd like to take it to the next level of wetsanding but I've never done it before and I'm a little leary about screwing it up or losing the smooth finish that could be waxed.

Anyhoo, any tips on cleaning up the dingy or dirty white deck top?